1. Field of the Invention
The present invention concerns a refrigeration cycle capacity enhancement apparatus, and particularly a refrigeration cycle capacity enhancement apparatus for applications in vehicle refrigeration cycles in which carbon dioxide gas is used as the coolant.
2. Description of the Related Art
In general, in a refrigeration cycle, a heat-exchanger is often provided for exchanging heat between low-pressure coolant at the outlet of an evaporator and high-pressure coolant at the intake of a condenser, thereby lowering the temperature of the coolant going from the condenser to the evaporator and raising the temperature of the coolant going from the evaporator to a compressor, enhancing the performance thereof, and seeking also to prevent the return of liquid coolant to the compressor.
In particular, in cases where carbon dioxide gas is used instead of conventional Freon as the coolant in the refrigeration cycle, Freon being problematic in that it destroys the ozone layer while carbon dioxide gas does not have that problem, a heat exchanger is well suited for enhancing the capacity of the refrigeration cycle, as noted above.
As to the heat exchanger, a double-pipe structure is effective, irrespective of the coolant type.
This heat exchanger will take on the functions of the condenser in an auxiliary capacity, so it is effective in lowering the high pressure of the coolant to some degree. However, when there is a high load on the refrigeration cycle, this is not adequate for circumventing high pressure rises in the coolant, which is a problem.
Meanwhile, there is another method for cooling high-pressure coolant in an auxiliary manner, namely that of introducing to the condenser the drain water from the evaporator that is discharged in abundance when there is a high load, as noted above, and exchanging heat between this and the coolant. However, there are problems with this also. Not only is the actual effective flow volume insufficient, with drain water alone, to cool the high-pressure coolant, but, particularly in refrigeration cycles used in vehicles, while the drain water is being conveyed to a condenser installed inside the engine compartment it absorbs heat from the engine compartment and evaporates, so that hardly any benefit can be hoped for.